Seaweed farming is often depicted as a sustainable form of aquaculture, but suspected habitat alterations and spread of algae outside farms have rendered speculations on the actual degree of sustainability. We conducted an experimental field study on Unguja Island (Zanzibar, Tanzania) to investigate the effects of off-bottom seaweed farming on a tropical seagrass ecosystem, using 1.5 × 2.5 m experimental farm plots. After 11 wk, above-ground seagrass biomass was 40% lower than in control plots, owing to a combination of lower shoot density, shoot length and leaf growth rate. Since the biomass was constant between Day 15 and 75 in the farm (F) treatment, but increased by 67 vs. 48% in the 2 controls (control treatment [C] and stick-and-line control treatment [CSL]), the effect exerted by the farm was a lack of potential biomass increase rather than an actual decrease. The effect was transplanted to associated organisms both in terms of lower seagrass epiphyte cover and changes in the abundance of 2 dominating epifauna taxa (>1 cm): sea urchins and sponges. Furthermore, the F treatment caused an accumulation of seagrass leaf litter, but did not affect sediment organic matter (SOM) content. The mechanisms behind these effects were not explicitly tested, but algal shading, emergence stress and mechanical abrasion were identified as likely contributors. Interestingly, the effects were largely restricted to 1 of the 2 seagrass species present, Enhalus acoroides, while the other, Thalassia hemprichii, remained more or less unaffected. This may be due to reduced interspecific competition or species-specific differences in morphology and stress tolerance, and could in the long-term have implications for (amongst others) associated fish communities. Although seaweed farming at the current level is less detrimental than, for example, intensive shrimp farming, and therefore should be seen as a strong option for future aquaculture developments, intensive farming on seagrasses should be avoided or at least minimized by, for example, implementing other farming methods. The risk of ecosystem-level changes in large-scale and uncontrolled farm enterprises warrants a holistic and integrated coastal management approach which considers all aspects of the tropical seascape including human societies and natural resource use.
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Organic extracts of 20 species of French seaweed have been screened againstTrypanosoma brucei rhodesiensetrypomastigotes, the parasite responsible for sleepingsickness. These extracts have previously shown potent antiprotozoal activitiesin vitroagainstPlasmodium falciparumandLeishmania donovani. The selectivity of the extractswas also evaluated by testing cytotoxicity on a mammalian L6 cell line. The ethylacetateextract of the brown seaweed,Bifurcaria bifurcata,showed strong trypanocidal activitywith a mild selectivity index (IC50= 0.53 μg/mL;selectivity index (SI)= 11.6). Bio-guidedfractionation led to the isolation of eleganolone, the main diterpenoid isolated from thisspecies. Eleganolone contributes only mildly to the trypanocidal activity of the ethylacetate extract (IC50= 45.0 μM, SI = 4.0). However,a selective activity againstP. falciparumerythrocytic stagesin vitrohas been highlighted (IC50= 7.9 μM, SI = 21.6).
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Centella asiatica is an endangered medicinal herb which used in the preparation of herbal drugs mainly due to the presence of four pentacyclic triterpene which are asiatic acid, asiaticoside, madecassic acid and madecassoside. It’s over exploitation necessitates the development of conservation strategies and enhanced the production of secondary metabolites. In present study, the effect of various concentration of seaweed Kappaphycus alvarezii elicitor was used to increase the amount of asiatic acid production in C. asiatica. Four difference concentration of seaweed elicitor was treated in C. asiatica which are 0 g/L, 2g/L, 4g/L and 8g/L. They are harvested at day 0, 7, 14 and 21 and soak with methanol to obtain crude brown extract. The amount of asiatic acid containing in the samples was analyzed by HPLC and area under the curve of retention peak was calculated by using a formula. The diameter of leaf, number of new shoots and flowers were measured during successive stages of development. In conclusion, K. alvarezii can increase the production amount of asiatic acid in C. asiatica at shorter time, which at day 14, concentration of 4g/L and 8 g/L are the best while the additional of certain concentrations of seaweed elicitor can induce flowering in C. asiatica
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Seaweeds are the renewable marine resources and they form the primary raw material for the agar and algin industries. They are mostly exploited from the south east coast of Tamil Nadu from Mandapam to Kanyakumari, Gujarat Coast, Lakshadweep islands and the Andaman and Nicobar islands. Even though substantial resources are available in our coastal waters, it is neither harvested to its fullest extent nor much efforts have been put forth. Seaweed collection renders extensive employment to the coastal fisher folk. The estimation of seaweed resources indicate that only a negligible quantity is harvested.
At present nearly 5000 women depend on the seaweed industries for their livelihood. If the available resources are harvested to its optimal level, it can provide employment to another 20,000 coastal fisher folk in harvesting sector and an equal number in post harvest activities. Since the domain of seaweed collecting industry is mainly dominated by women, special efforts should be taken for its optimum exploitation and market expansion through diversified product development and their popularization. This paper deals with the employment potential offisherwomen in seaweed industries, problems and prospects in the collection and processing segments of seaweeds.
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With increasing demand for resources to achieve global food-water-energy nexus and rapid decline in land-based sources, oceans represent both solution and boost to sustainable environment and economy. In addition to fundamental part of earth’s ecosystem for uncatalogued diversity of life, oceans are undervalued economy powerhouse with gross marine product value. With sustainable management of existing assets including ship- ping, transportation, manufacturing, fisheries, tourism and exploration of new business like marine biotech- nology and renewable energy, the ocean or blue economy has potential to fulfill sustainable development goals (SDG). In spite of recognition of blue economy as a new economic frontier, investments by existing industries and emergence of new ones are limited and less known, hence require more in depth attention and scientific un- derstanding. In the present study, authors present a systematic comparative assessment of blue economy sectors with distinct challenges and strategies to be further explored and implemented for industrial deployment. The conceptualization of integrated routes of bio(economy) by the current study can act as gateway for key stake- holders, i.e. governance, bluepreneurs (scientists and industries) to prioritize technologies for sustainable ap- plications of marine resources.
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This chapter provides a brief overview of some of the major steps in the development of microalgae-based processes for renewable energy production. The chapter attempts to highlight the development and evolution of the key concepts and research in the field, preparing the reader for the following chapters, which will deepen the discussion on the subject.
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Macroalgae, commonly known as seaweed, has received significant interest as a potential source of ethanol because of its fast growth, significant sugar content and successful lab-scale conversion to ethanol. Issues such as energy input in seaweed conversion, lifecycle emissions, global production potential and cost have received limited attention. To address this gap, a well-to-tank model of ethanol production from brown seaweed is developed and applied to the case of ethanol production from Saccharina latissima in British Columbia, Canada. Animal feed is proposed as a co-product and co-product credits are estimated. In the case considered, seaweed ethanol is found to have an energy return on invested (EROI) of 1.7 and a carbon intensity (CI) of 10.8 gCO2e MJ 1. Ethanol production from conventionally farmed seaweed could cost less than conventional ethanol and be produced on a scale comparable to 1% of global gasoline production. A drying system is required in regions such as British Columbia that require seasonal seaweed storage due to a limited harvest season. The results are significantly influenced by variations in animal feed processing energy, co-product credit value, seaweed composition, the value of seaweed animal feed and the cost of seaweed farming. We find EROI ranges from 0.64 to 26.7, CI from 33 to 41 gCO2e MJ1 and ethanol production is not financially viable without animal feed production in some scenarios.
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The cultivation of seaweed as a feedstock for third generation biofuels is gathering interest in Europe, however, many questions remain unanswered in practise, notably regarding scales of operation, energy returns on investment (EROI) and greenhouse gas (GHG) emissions, all of which are crucial to determine commercial viability. This study performed an energy and GHG emissions analysis, using EROI and GHG savings potential respectively, as indicators of commercial viability for two systems: the Swedish Seafarm project's seaweed cultivation (0.5 ha), biogas and fer- tilizer biorefinery, and an estimation of the same system scaled up and adjusted to a cultivation of 10 ha. Based on a conservative estimate of biogas yield, neither the 0.5 ha case nor the up-scaled 10 ha estimates met the (commercial viability) target EROI of 3, nor the European Union Renewable Energy Directive GHG savings target of 60% for biofuels, however the potential for commercial viability was substantially improved by scaling up operations: GHG emissions and energy demand, per unit of biogas, was almost halved by scaling operations up by a factor of twenty, thereby approaching the EROI and GHG savings targets set, under beneficial biogas production conditions. Further analysis identified processes whose optimisations would have a large impact on energy use and emissions (such as anaerobic digestion) as well as others embodying potential for further economies of scale (such as harvest- ing), both of which would be of interest for future developments of kelp to biogas and fertilizer biorefineries.
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Biochar, a pyrogenic black carbon is derived by pyrolysis of carbon-rich biomass in an oxygen-limited environ- ment. The physico-chemical characteristics of biochar strongly impact the multifunctional role of biochar e.g., carbon sequestration and enhancement of soil fertility, biosorption or environmental remediation, fuel cells, supercapacitors, and biocatalyst. Owing to the poor performance of pristine biochar, engineered biochars have emerged, that are derived from physical, chemical, and biological modifications of pristine biochar to im- prove its surface properties and thus adsorption capacity. In the past two decades, researchers have been focus- sing more on low-cost biomass. Algal biomass is one such source that has shown significant prospective for biochar fabrication. The present review summarizes various applications of biochar, mechanisms associated with metal removal by biochar, various modification procedures for developing engineered biochars, algal bio- char production methods as well as characterization of algal biochar. The review is intended to evaluate recent advancements and research in engineered algal biochar with a primary focus on contaminant remediation and the development of bioelectrochemical systems using algal biochar. This review opens new vistas and adds inno- vative ideas for future research utilizing engineered algal biochar, towards renewable, sustainable, and low-cost production of biosorbents for remediation of contaminated aqueous environments.
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The increasing cost of synthetic fertilizers and conventional agrochemicals calls for an urgent search for next generation of environmental-friendly competitive fertilizers and growth stimulants that enhance the essential oil content and composition of traditional global medicinal plants such as mint (Men- tha×piperita L.“chocolate”) and sweet basil (Ocimum basilicum L. “purple ruffle”). The study aims to evaluate the morphological and physiological effects of seaweed extracts (Ascophyllum nodosum) doses and application methods on mint and basil plants essential oil composition and its respective antibacte- rial activities. The plants were subjected to two doses of foliar/drench weekly applications of A. nodosum extracts at 5 and 7 mL L−1 for 12 weeks. A. nodosum extracts drench and foliar treatments increased leaf number and area, dry weights, and plant height of both plants. In mint and basil plants, there were increases in the essential oil content and enhanced composition following A. nodosum treatments. In mint plants, the drench application of 7 mL L−1 SWE had the highest oil contents of l-menthone (32.4%) and l-menthol (32.6%) while basil treated plants showed the highest composition of chavicol methyl ether (38.7%), linalool (29.1%), and cineol (9.1%). Additionally decreasing of potentially toxic pulegone and methofuran in mint oil was noticed. A. nodosum treated plants showed higher antibacterial poten- tial than control. In mint and basil plants, the highest antibacterial activity found was in the essential oil of mint plants drenched with 7 mL L−1 SWE and the antibacterial activities of mint oils were higher than basil. The biostimulant effect of A. nodosum extract treatments was attributed to the macro- and micro-elements composition as well as the carbohydrate contents.
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